relates to terminal connector heads and more particularly to terminal connector heads used with temperature sensors.
Terminal connector heads are frequently used with temPerature sensors. A temperature sensor typically comprises a temperature sensing element, such as a thermocouple, encased in a protection tube. The sensing element provides or varies an electrical signal which is indicative of temperature. This electrical signal is transmitted to a process instrument which translates it into usable information. Such a process instrument might be a digital readout or an analog/digital converter.
Terminal connector heads must usually be used with temperature sensors because the sensing element typically has short lead wires. Consequently, these lead wires must be connected to other wires which are then run back to the process instrument. This interconnection is done in a terminal connector head and by the terminals and terminal strips in the terminal connector head.
The terminal connector head must be designed to withstand the environmental conditions which exist where it is mounted. Since it must typically be mounted very close to the process which is being sensed by the sensing element, these environmental conditions can be severe. For example, if a temperature sensor is used to sense high temperatures such as exist in furnaces, the terminal connector head can be exposed to very high temperatures.
Heretofore, terminal connector heads have typically comprised a housing with a cover. In one type of terminal connector head, a terminal block is mounted in the housing. In another type, the housing is formed with integral terminal strips. That is, holes are formed in the housing which receive threaded inserts. The terminal screws of the terminal strips are threaded into the threaded inserts.
The lead wires from the sensing element are run through a process opening in the housing and affixed to terminals of a terminal strip. For example, if the temperature sensing element has two lead wires, each lead wire would be attached to one terminal of respective two-terminal terminal strips. The other terminal of each terminal strip is connected to the process instrument by an appropriate type of wire which is typically run through a conduit.
Ceramic terminal blocks must sometimes be used to provide the necessary degree of insulation. In some cases, the thermoplastics which are temperature-resistant plastics of which the housing can be made do not provide sufficient insulation or temperature resistance.
Heretofore, the terminal connector heads have been one or the other of the above-described types. That is, they have either been a terminal connector head in which a terminal block is mounted in a housing or a terminal connector head having a housing with integral terminal strips. There has not been a terminal connector head which can interchangeably be either type.
It is an object of this invention to provide a terminal connector head having a housing with integral terminal strips in which a terminal block can be mounted.
It is another object of this invention to provide a terminal connector head that has terminals formed as integral parts of the housing wherein a terminal block can be mounted in the housing by using the holes formed in the housing for the integral terminals.
It is another object of this invention to provide a terminal connector head which is interchangeable between a terminal connector head with integral terminal strips and a terminal connector head in which a terminal block is mounted.
According to the present invention, a terminal connector head has a housing and a cover. The cover is removably mounted on the housing. The housing has an inner surface that has holes formed therein. The holes receive threaded inserts into which terminal screws are threaded. The holes are formed in pairs to provide for terminal strips. That is, two terminal screws are threaded into the threaded inserts in each pair of holes with a connecting link extending therebetween. The holes are located in the inner surface of the housing such that one or more of the threaded inserts in the holes will match holes or slots in a terminal block. The terminal block can then be mounted in the housing by using the threaded inserts which match up with the holes or slots in the terminal block. Illustratively, the terminal block has slots on either side. Each slot matches up with a threaded insert in one of the holes formed in the inner surface of the housing.